Arihant is one who is present in one of the 15 karma bhumis, has a body like ours and through self effort renounces the world, gets rid of the intense (ghati) karmas and attains omniscience. Only then do they preach the religion to the masses. At present, there are no Arihants on earth. The last one was Lord Mahaveer about 2500 years ago. Jains believe that there are currently 20 Tirthankaras (of which Simmandhar Swami is widely known) in another world called Mahavideha Kshetra.
There could be other souls such as their disciples who also attain omniscience, but they are called Kevalis and not Tirthankars. The main distinction is that Tirthankaras establish a four fold sangh and preach religion to the masses which the Kevalis do not. Thus, one can consider Arihants as patriarchs of the entire sangh and thought of as “God – the Father” who are an embodiment of universal welfare.
When the lifespan of the Tirthankars (or Kevalis for that matter) is over, they become Siddha. Christians consider Spirit to be God’s continuous presence on Earth. Jains believe that the nature of the Holy Spirit (Siddha’s soul) is the same as the soul of all living beings present in the Universe. The only difference is in the degree of purity. Siddha’s soul exists in its pure form for all eternity without a body and no karmic matter attached to it. All mundane souls need to purify their souls and free itself from the karmic bondage and truly become an eternal, everlasting “spirit” (pure soul → Siddha).
In the absence of a living Tirthankar, the ascetics are the ones who preach the religion to the laity. The trinity of Ācharyās, Upadhyāyas and Sādhus can be considered as the “sons” of God as they are the ones who represent the teachings of Arihants and currently propound the religion.
* Ācharyās are heads of the congregation.
* Upadhyāyas are adept in knowing and teaching the Jain scriptures.
* All ascetics who take the 5 Māhāvrata vows are called Sādhus (monks) / Sādhvis (nuns).